Reading a vector of double from a TTree in a root file

[Heng_Fai_Chang]

Hello,

I encountered some troubles when using the following command in my script to read a vector of double Jet_pt from a TTree in an external root file.

void MyMacro() {
…
…
std::vector *Jet_pt;
…
…

TFile f(“file_name.root”);
TTree lfv = (TH1F*) f->Get(“lfv”);
lfv -> SetBranchAddress (“Jet_pt”, &Jet_pt"); //This is where the excution stopped with segmentation fault
…
…
}

lfv is a TTree with a branch called “Jet_pt” which is a vector of double and its name coincided with the variable declared in my script.

Would you guys mind help me investigate the issue?

Many thanks for the help
Johnny

[behrenhoff]

Initialize your variables!

std::vector<Double_t> *Jet_pt = nullptr;

Or, as an alternative, create a vector with new.

By the way, this line:[quote=“Heng_Fai_Chang, post:1, topic:24358”]
TTree* lfv = (TH1F*) f->Get(“lfv”);
[/quote]
is very wrong. This does not even compile.

[Heng_Fai_Chang]

Hi behrenhoff

Many thanks! The issue of segmentation fault was fixed after adding the initialization.